Baffle type muffler with refractory lining



Sept. 26, 1950 J. M. CAMPBELL BAF'F LE TYPE MUFF'LER WITH REFRCTORY LINING Filed March 28, 1946 Patented Sept. 26, 1950 BAFFLE TYPE MUFFLER WITH REFRACTORY LINING John M. Campbell, Cleveland, Ohio, assignor to John M. Campbell and Philmore J. Haber, as

trustee Application March 28, 1946, Serial No. 657,643

11 Claims.

This invention relates to mulliers, particularly to a muffler for internal combustion engines.

An object of the invention is to provide a muffier which combines a high degree of sound absorption with a minimum of interference to ilow of gases.

Another object of the invention is to provide a muffler employing sound absorbing material having sufficient strength to make possible the elimination of liners in the muliler chambers.

A further object of the invention is the provision of a muffler which will have a high degree of resistance to vibration, heat, and chemical acn tion.

A still further object of the invention is the provision of a muffler which, though highly effective, is particularly adapted to economical production.

A still further object of the invention is a muffler in which provision is made for reducing the transmission of sound through a mass of porous sound absorbing material.

Other objects and advantages more or less ancillary to the foregoing and the manner in which all the various objects are realized will appear in the following description, which, considered in connection with the accompanying drawings, sets forth the preferred embodiment of the invention.

Referring to the drawings:

Fig. 1 is a longitudinal section of a muffler embodying the principles of the invention;

Fig. 2 is a transverse section taken on the plane indicated by the line 2 2 in Fig. 1; and

Fig. 3 is a partial longitudinal section taken on the plane indicated by the line 3-3 in Fig. 2.

Mufiiers, as generally known in the art, depend, by and large, for their action upon baliles placed in the path of gas flow, on resonance chambers, on the use of a sound absorbing material of a porous material, or upon a combination of two or more of these principles.

The improved muffler described herein depends for its action upon a combination of the principles of baffling, resonance, and absorption. The invention lies in the novel design of the muffler,

Awhich provides for the effective operation of all three of these principles while retaining simplicity, -ease of construction, ruggedness, and a minimum of resistance to the iiow of gas.

Referring rst, to Fig. 1, the muffler of the preferred embodiment of the invention is encased in a cylindrical sheet metal shell II, and end caps I2 and I3, spot-welded or otherwise secured thereon. A thin Walled tube I4, disposed along the axis of the shell, is mounted in flanges formed in the center of the end caps I2 and I3. The open ends I5 and i6 of the tube I4, constitute inlet and outlet ports of the muffler, respectively. The tube I4 is provided with a number of elongated openings Il, Within the shell Il. Four rows of eight such openings, as shown, have been found to be a desirable arrangement. It is, of course, possible to vary the number and shape of the openings, varying the size accordingly. Whatever the number of the openings, the total area should not be less than twice the cross-'sectional area of the inlet I5.

The muffler includes a plurality of main or gasreceiving and conducting chambers. For example, the tube I4 is divided into an inlet chamber I4@ and an outlet chamber I4b by a conical deflector I8, which completely blocks the tube at its central point. The deflector I8 is iilled with sound absorbing material such as a composition formed principally of exfoliated vermiculite with a binder of clay; however, other sound absorbing matem rials known to the art, such as steel Wool, spun glass, and rock wool, with or without a binder, may be employed. The deflector I8 and the disc I9, which serves as a retainer for the dei-lector, are secured in the tube I4 by spot welding or in any other suitable manner.

The shell I I is provided with a liner 2l of sound absorbing material, preferably eXfoliated vermiculite with a binder of a character that may be handled in a plastic state during the manufacture of the muffler, It is an object of the invention to employ a material having sufficient strength to serve as a substitute for liners of a perforated metal or wire screen, such as are commonly employed in the art. Such liners not only increase the complexity and expense of construe tion of the muffler, but decrease the effectiveness of the sound absorbing materials, increase the resistance to gas ilow, and are subject to damage from the corrosive action of the hot exhaust gases. A composition of eXfoliated vermiculite, clay, and other materials, such as is disclosed in my copending applications Nos. 593,964 and 593, 963 iiled May 15, 1945, now Patent Numbers 2,481,391 and 2,481,390, respectively, issued September 6, 1949, is the preferred material for lining the shell I I and the deflector I8. It has sufcient mechanical strength, resistance to heat, corrosion, and scouring action, and high sound absorption, and does not calcine or vitrify under temperatures reached in an internal combustion engine muffler. The liner 2I is formed to completely line the shell I I and the end cap I2, and also provide a plurality of roughly semicircular gas-receiving and sound-absorbing chambers 24 (Fig. 2) extending in contiguous relationship to the tube I4. Each chamber 24 communicates with the inlet and outlet chambers Ilia and Ilib through the openings I'i.

In order to reinforce the lining material 2i, longitudinal fins protrude outward from the tube I4 into the septa between the cavities 24. The fins 25 are formed with a flange 26, bent to support the major body of the fin in radial relation to the tube when welded in place thereon. The ends 2? of the flanges extend beyond the n end, as shown in Fig. 3, are inserted in slots 21a in the tube then doubled back against the inner wall of the tube to provide a temporary anchorage for the part during the spot welding operating.

The foraminous liner 2| has formed therein as at 28 a plurality of secondary chambers 23 (Fig. 2) extending from the end cap I2 to the rear end of chambers 2li provided in the liner 2l. The secondary chambers 28 are of appreciable cross-sectional area as compared with the interstices between the foraminous particles and minimize the conduction of sound therethrough and dampen the vibrations transmitted to the shell il. The rear ends of the chambers 24 and the secondary chambers 28 are closed by an annular disk 22, the intermediate space being filled with a sound absorbing material of the character employed in liner 2l.

As will be seen in Fig. 2, the material of tube I4 is deformed at the edges of the slots I'I. One side of each slot is distended outwardly while the other side thereof is depressed. By virtue of this structure, the gases leaving the tube are biased relative to the radius thereof, thus producing substantial turbulence in the chambers 24.

In the preferred method of constructing the muier, the shell II, the end cap I2, the central tube I4, and the deflector I8, I9 are first brought into assembled relation. The material of the liner 2l, while in a plastic condition, is forced into place into the void dened by the shell and the central tube, a moulding form or core being provided to denne the chambers 24 and secondary chambers 2S. The annular disk 2! is next put in place, then a lining material 23 is applied thereover whereupon the end cap I3 is mounted in place and welded to the tube and shell. The muier is then dried to harden the lining material 2U, 2l, and 23.

In the operation of the improved muffler, gases entering the chamber Ifla at the opening I5, pass through the slots Il into the plurality of parallel chambers 24 wherein sound waves are absorbed by the porous material 2l. The gases then pass through the slots l? into the outlet chamber I4b formed by the outer portion of tube I4. It will be seen that the flow of gas is deflected and baffled as it passes into the sound-absorbing chambers 24 and as it is discharged therefrom. A certain amount of resonant action takes place both in tube I4, and in the sound-absorbing chambers 24, absorption of the vibrations being accomplished by the liner 2l of chambers 24. The deector IB secures a more uniform distribution of the gas as it passes into chambers 24 through slots I'! and the absorbing material therein minimizes direct transmission of sound between the chambers I la and leb. In addition, the entire inner opening of the muffler, that is, the chambers Illa, I4b, and 24, constitutes one gas-receiving and conducting chamber of irregular form in which sound may reverberate, being partially reflected by the wall of the tube I4 and partially passing through the openings I'l.

Although the foregoing description is necessarily of a detailed character, in order that the invention may be completely set forth, it is to be understood that the specic terminology is not intended to be restrictive or confining, and that various rearrangements of parts and modications of detail may be resorted to without departing from the scope or spirit of the invention as herein claimed.

I claim:

1. A muffler comprising a tube, an obstruction in the tube dividing it into intake and outlet portions, a shell surrounding the tube, and a lining of porous refractory material within the shell formed to provide a plurality of gas-receiving chambers, each chamber extending longitudinally of the exterior of both portions of the tube, both portions of the tube being provided with slots communicating with each chamber, the slots being disposed longitudinally of the tube, the

material of the tube adjacent the slots being bent radially outwardly so as to direct gas flow through the slots obliquely to the radius of the tube.

2. A muffler comprising a tube, an obstruction in the tube dividing it into intake and outlet portions, a shell surrounding the tube, and a linof porous refractory material within the shell formed to provide a plurality of chambers, each chamber extending longitudinally of the exterior of both portions of the tube, both portions of the tube being provided with slots communicating with each chamber, the obstruction being a conical shell having its apex directed into the intake portion and being filled with a porous refractory material.

3. A muffier comprising a tube, an obstruction in the tube dividing it into intake and outlet portions, a shell surrounding the tube, and a lining of porous refractory material Within the shell formed to provide a plurality of chambers extending longitudinally of the exterior of the tube, both portions of the tube being provided with per- 1 orations communicating with each chamber, and the tube being provided with longitudinal ns extending into the refractory material between the chambers.

4. In a muflier, a gas-receiving and sound-absorbing chamber having a minor part of its wall area formed by a perforate non-absorbent material through which gas flows into and out of the chamber, and having a major part of its wall area formed by a thick envelope of a foraminous self-supporting refractory material, said envelope having a plurality of secondary chambers formed therein and isolated from said gas-receiving chamber.

5. In a muiiier, a gas-receiving and sound-absorbing chamber having a minor part of its wall area formed by a perforate non-absorbent material through which gas flows into and out of the chamber, and having a major part of its wall area formed by a thick self-supporting envelope composed of exfoliated vermiculite and a binder therefor, said envelope having secondary chambers formed therein and isolated from said gasreceiving chamber.

6. In a muffler, a shell, and a lining of porous rigid refractory material within the shell formed to define at least one gas-receiving and soundabsorbing chamber within the lining, the lining being formed to denne a plurality of secondary chambers disposed intermediate the shell and chamber, said secondary chambers also constituting sound-absorbing cavities to dampen the transmission of vibrations through the lining, and being isolated from the flow path through the muiiier.

7. In a muffler, a gas-receiving and sound-absorbing chamber having a minor part of its wall area formed by a periorate non-absorbing material 'through which gas fiows into and out of the chamber, and having a major part of its wall area formed by a thick envelope of porous rigid refractory material having secondary chambers formed therein isolated from the gas-receiving chamber, said secondary chambers forming sound-absorbing cavities to dampen the transmission o vibrations through the material.

8. In a muier, a shell, a plurality of parallel gas-receiving and sound-absorbing chambers within the shell, each having a minor part of its wall area formed by a perforate non-absorbing material through which gas ow into and out of the chamber is accomplished, and having a major part of its Wall area, including the wall between adjacent chambers, formed by a thick envelope of a porous rigid refractory material,

said refractory material having isolated secondary chambers formed therein between the gasreceiving chambers and the shell.

9. In a muiiier, a shell, a porous self-supporting lining composed of exfoliated vermiculite and a binder within the shell, the lining being formed to define a gas-receiving and sound-absorbing chamber therein, a closed slotted tube section entering the chamber for the admittance of gases, a closed slotted tube section entering the chamber for the discharge of gases, the slots in the tube section being formed to direct the flow of gas obliquely to the radius of the tube sections, and anchoring means extending from the tube sections into the lining, said lining having closed secondary chambers formed therein.

l0. A mufer comprising a tube, an obstruction in the tube dividing it into intake and outlet portions, a shell surrounding the tube, and a lining of porous refractory material within the shell formed to provide a, plurality of chambers,Y

6 each chamber extending longitudinally of the exterior of both portions of the tube, both portions of the tube being provided with slots communicating with each chamber.

11. A muffler comprising a tube, an obstruction in the tube dividing it into intake and outlet portions, a shell surrounding the tube, and a lining of porous refractory material Within the shell formed to provide a plurality of chambers, each chamber extending longitudinally of the exterior of both portions of the tube, both portions of the tube being provided with slots communicating with each chamber, the slots being disposed longitudinally of the tube, the material of the tube being formed adjacent the slots so as to direct gas flow through the slots obliquely to the radius of the tube by forming the material of the tube so that one edge of each slot is farther removed from the axis of the tube than the other edge of the slot so that the aperture defined by the tedges of the slot is oblique to the radius of the ube.

JOHN M. CAMPBELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 963,822 Smith July 12, 1910 1,777,522 Hamilton Oct. 7, 1930 1,909,511 Wilson May 16, 1933 1,912,544 Slidell June 6, 1933 1,927,213 MacKenzie et al. Sept. 19, 1933 2,009,343 Peik July 23, 1935 2,065,343 Moore et al Dec. 22, 1936 2,072,961 Nelson Mar. 9, 1937 2,166,417 Manning July 18, 1939 FOREIGN PATENTS Number Country Date 191,766 Switzerland Sept. 16, 1937 350,031 Italy July 3, 1937 449,507 Great Britain June 29, 1936 495,576 Great Britain Nov. 16, 1938 881,494 France Apr. 27, "1943 

